[Payments] Add combobox support to editors.

chrome/browser/ui/views/payments/validating_combobox.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/ui/views/payments/validating_combobox.h"
+
+#include <utility>
+
+namespace payments {
+
+ValidatingCombobox::ValidatingCombobox(
+    std::unique_ptr<ui::ComboboxModel> model,
+    std::unique_ptr<ValidationDelegate> delegate)
+    : Combobox(std::move(model)),
+      delegate_(std::move(delegate)),
+      was_blurred_(false) {}
+
+ValidatingCombobox::~ValidatingCombobox() {}
+
+void ValidatingCombobox::OnBlur() {
+  Combobox::OnBlur();
+
+  // The first validation should be on a blur. The subsequent validations will
+  // occur when the content changes.
+  if (!was_blurred_) {
+    was_blurred_ = true;
+    Validate();
+  }
+}
+
+void ValidatingCombobox::OnContentsChanged() {
+  // Validation on every keystroke only happens if the field has been validated
+  // before as part of a blur.
+  if (!was_blurred_)
+    return;
+
+  Validate();
+}
+
+void ValidatingCombobox::Validate() {
+  // ValidateCombobox may have side-effects, such as displaying errors.
+  SetInvalid(!delegate_->ValidateCombobox(this));
+}
+
+}  // namespace payments